[captn3m0]

This is what GNU Taler [0] does. You can send additional headers[1] to decide how the payment will be processed, such as X-Taler-Contract-Url and X-Taler-Offer-Url

[1]: https://docs.taler.net/merchant/frontend/python/html/tutoria...

[0]: https://taler.net/en/index.html